That's a thought Anneza - thanks for the suggestion. I'll do a bit more research in that area. Here's what I have found so far.
It could certainly be a form of the Italian Neroli which may mean Orange Blossom but is most often listed as the name of an Italian princess. Nera means Black in Italian too. However it is uncommon for Australians to take to Italian names so readily.
If we look to Celtic/English options we can find Ner meaning Lord, Nera meaning Lady and Leigh meaning Meadow/Field/Clearing. So Neralie could mean Lady of the Meadow or similar. There is a celtic myth about a man named Nera which might be a good reason to think the name could be Celtic.
Nera is also Greek for Water. Neralie could possibly combine Nera and Leon (lion) to mean something like Lion of the Ocean/Sea.
Nera is Indo-European for Strength and Power
Nera is old Hebrew for Lamp and Leah means Weary or Mistress/Ruler. Ruler of the Lamp perhaps? Many of our names are Hebrew in origin.